1. Field of the Invention
The present invention relates generally to an electrical coaxial connector, and more particularly to an improvement in an electrical coaxial connector to be mounted on a circuit board for transmitting signals from the circuit board to the outside thereof or to the circuit board from the outside thereof under a condition of electro-magnetic shield.
2. Description of the Prior Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
A high-frequency signal flowing through conductors arranged on a circuit board is mostly dealt with as a signal which requires to be put in a condition of electro-magnetic shield so as to be inactive to leak out from the conductors or to prevent noises from mixing into the signal from the outside when the high-frequency signal is transmitted from the circuit board to the outside thereof or to the circuit board from the outside thereof. For transmitting the high-frequency signal from a specific circuit board to the outside thereof, for example, to another circuit board, or to the specific circuit board from the outside thereof, for example, from another circuit board, under the condition of electro-magnetic shield, an electrical coaxial connector to be mounted on the specific circuit board is used.
Such an electrical coaxial connector comprises usually an insulating base, a signal-joining contacting conductor provided on the insulating base for transferring a signal and a grounding contacting conductor provided on the insulating base for surrounding the signal-joining contacting conductor to be supplied with a ground potential so as to put the signal supplied to the signal-joining contacting conductor in a condition of electro-magnetic shield. When the electrical coaxial connector is mounted on a circuit board to be put to practical use, the electrical coaxial connector is coupled with a mating coaxial connector which is, for example, another electrical coaxial connector mounted on another circuit board, so that the signal-joining contacting conductor comes into contact with a signal-joining conductor provided in the mating coaxial connector and the grounding contacting conductor comes into contact with a grounding conductor provided in the mating coaxial connector. With the electrical coaxial connector and the mating coaxial connector coupled with each other in such a manner, the signal supplied to the signal-joining contacting conductor of the electrical coaxial connector or to the signal-joining conductor of the mating coaxial connector is transferred to the signal joining conductor of the mating coaxial connector or to the signal joining contacting conductor of the electrical coaxial connector under the condition of electro-magnetic shield brought about by the grounding contacting conductor of the electrical coaxial connector and the grounding conductor of the mating coaxial connector. Thereby, the signal is transmitted between the circuit boards, on which the electrical coaxial connector and the mating coaxial connector are mounted respectively, under the condition of electro-magnetic shield.
When the electrical coaxial connector as mentioned above is mounted on the circuit board, the signal-joining contacting conductor is connected with a signal terminal provided on the circuit board and the ground-connecting contacting conductor is connected with a ground-potential terminal provided on the circuit board. Then, a condition wherein the signal-joining contacting conductor connected with the signal terminal provided on the circuit board and the ground-connecting contacting conductor connected with the ground-potential terminal provided on the circuit board are properly and surely connected respectively with the signal-joining conductor of the mating coaxial connector and the grounding conductor of the mating coaxial connector, is desired to be stably maintained for a relatively long period of time.
There has been proposed to provide an improved electrical coaxial connector which comprises an isolating base, a signal-joining contacting conductor provided on the insulating base and a grounding contacting conductor provided on the insulating base to surround the signal-joining contacting conductor and in which the signal-joining contacting conductor is so contrived in its structure that a condition wherein the signal-joining contacting conductor is connected with a signal-joining conductor of a mating coaxial connector is improved to be put in better maintenance, as disclosed in, for example, the Japanese patent application published before examination under publication number 2009-104836.
The previously proposed electrical coaxial connector disclosed in the publication mentioned above comprises a signal-joining contacting conductor (a socket type central conductor (22)) provided to be electrically connected with a signal-joining conductor (a pin type central conductor (12)) of a mating coaxial connector (a receptacle connector (11)), an insulating base (a second insulating housing (24)) mounted on a circuit board (a second board (2)) for supporting at its central portion the signal-joining contacting conductor, and a grounding contacting conductor (a second cylindrical conductor (23)) formed into a cylindrical shape for surrounding the insulating base supporting the signal-joining contacting conductor on the circuit board. The signal-joining contacting conductor has a top end portion made of a metallic tube and the signal joining conductor of the mating coaxial connector is inserted into the top end portion of the signal joining contacting conductor when the signal-joining contacting conductor is connected with the signal-joining conductor of the mating coaxial connector.
Further, four slits (27) are provided on the top end portion of the signal-joining contacting conductor in such a manner that each of the slits extends in parallel with an imaginary central axis of the metallic tube constituting the top end portion of the signal-joining contacting conductor. These four slits are arranged at regular intervals for surrounding the imaginary central axis of the metallic tube and an end portion of each of the slits reaches to a top end of the metallic tube in a direction along the imaginary central axis thereof. Accordingly, the top end portion of the signal-joining contacting conductor is divided into four parts by the four slits so as to be provided with four divided parts each extending in parallel with the imaginary central axis of the metallic tube.
On the top end portion of the signal joining contacting conductor constituted with the metallic tube and divided by the four slits to have the four divided parts, each of the four divided parts of the top end portion of the signal-joining contacting conductor is provided to be movable resiliently for coming close to or going away from the imaginary center axis of the metallic tube. Thereby, each of the four divided parts of the top end portion of the signal-joining contacting conductor comes into press-contact with the signal-joining conductor of the mating coaxial connector to exert resilient pressure on the same when the signal-joining conductor of the mating coaxial connector is inserted into the top end portion of the signal-joining contacting conductor. Consequently, it is expected that the condition wherein the signal-joining conductor of the mating coaxial connector is inserted into the top end portion of the signal-joining contacting conductor so that the signal joining contacting conductor is electrically connected with the signal joining conductor of the mating coaxial connector is able to be surely and stably maintained.
In the above-mentioned previously proposed electrical coaxial connector in which the signal joining contacting conductor has the top end portion constituted with the metallic tube into which the signal-joining conductor of the mating coaxial connector is inserted and provided with the four divided portions each extending in parallel with the imaginary central axis of the metallic tube, in order to maintain stably the condition wherein the signal joining conductor of the mating coaxial connector is inserted into the top end portion of the signal-joining contacting conductor so that the signal joining contacting conductor is electrically connected surely and properly with the signal-joining conductor of the mating coaxial connector, the four divided parts of the top end portion of the signal joining contacting conductor are required to exert relatively large resilient pressure to the signal-joining conductor of the mating coaxial connector. Then, each of the four divided parts of the top end portion of the signal-joining contacting conductor is required to have a relatively large length in the direction along the imaginary central axis of the metallic tube for increasing the resilient pressure exerted on the signal joining conductor of the mating coaxial connector by the four divided parts of the top end portion of the signal-joining contacting conductor. In the case where each of the four divided parts of the top end portion of the signal joining contacting conductor is not configured to have the relatively large length in the direction along the imaginary central axis of the metallic tube, the condition wherein the signal-joining conductor of the mating coaxial connector is inserted into the top end portion of the signal joining contacting conductor is not surely and stably maintained.
When each of the four divided parts of the top end portion of the signal-joining contacting conductor is configured to have the relatively large length in the direction along the imaginary central axis of the metallic tube, a portion of the signal-joining contacting conductor projecting from the insulating base is not able to be reduced in its length. As a result, it is difficult to reduce a measure of thickness of the electrical coaxial connector which comprises the signal-joining contacting conductor, the insulating base mounted on the circuit board for supporting the signal-joining contacting conductor and the grounding contacting conductor formed to surround the insulating base so that the electrical coaxial connector is prevented from making a relatively large projection on the circuit board. Therefore, although it has been desired for the electrical coaxial connector to be mounted on the circuit board to have a reduced measure of thickness, especially, in the field of relatively small-sized electronic apparatus in which a down-sized circuit board on which various kinds electronic parts are highly integrated is employed, such desire has not been sufficiently fulfilled.